1. Field of the Invention
This invention relates generally to semiconductor products manufacturing, and, more particularly, to a method and apparatus for compensation of process control in response to machine disturbances for run-to-run control of semiconductor manufacturing processes.
2. Description of the Related Art
The technology explosion in the manufacturing industry has resulted in many new and innovative manufacturing processes. Today""s manufacturing processes, particularly semiconductor manufacturing processes, call for a large number of important steps. These process steps are usually vital, and, therefore, require a number of inputs that are generally fine-tuned to maintain proper manufacturing control.
The manufacture of semiconductor devices requires a number of discrete process steps to create a packaged semiconductor device from raw semiconductor material. The various processes, from the initial growth of the semiconductor material, the slicing of the semiconductor crystal into individual wafers, the fabrication stages (etching, doping, ion implanting, or the like), to the packaging and final testing of the completed device, are so different from one another and specialized that the processes may be performed in different manufacturing locations that contain different control schemes.
Among the factors that affect semiconductor processing are machine disturbances. Machine disturbances include external factors such as temperature, humidity, and idle time between processes. One area of semiconductor manufacturing that is affected by machine disturbances is overlay process. One of the most important aspects of semiconductor manufacturing is overlay control. Overlay is one of several important steps in the photolithography area of semiconductor manufacturing. Overlay control involves measuring the misalignment between two successive patterned layers on the surface of a semiconductor device. Generally, minimization of misalignment errors is important to ensure that the multiple layers of the semiconductor devices are connected and functional. As technology facilitates smaller critical dimensions for semiconductor devices, the need for the reduction of misalignment errors increases dramatically.
Generally, photolithography engineers currently analyze the overlay errors a few times a month. The results from the analysis of the overlay errors are used to manually make updates to exposure tool settings. Some of the problems associated with the current methods include the fact that the exposure tool settings are only updated a few times a month. Currently the exposure tool updates are performed manually. Machine disturbances can also change the effectiveness of control settings.
Generally, a set of processing steps is performed on a lot of wafers on a semiconductor manufacturing tool called an exposure tool or a stepper. The manufacturing tool communicates with a manufacturing framework or a network of processing modules. The manufacturing tool is generally connected to an equipment interface. The equipment interface is connected to a machine interface to which the stepper is connected, thereby facilitating communications between the stepper and the manufacturing framework. The machine interface can generally be part, of an advanced process control (APC) system. The APC system initiates a control script, which can be a software program that automatically retrieves the data needed to execute a manufacturing process. The input parameters that control the manufacturing process are revised periodically in a manual fashion. As the need for higher precision manufacturing processes are required, improved methods are needed to revise input parameters that control manufacturing processes in a more automated and timely manner. Furthermore, efficient compensation for machine disturbances is needed.
The present invention is directed to overcoming, or at least reducing the effects of, one or more of the problems set forth above.
In one aspect of the present invention, a method is provided for correction of machine disturbances for run-to-run control of semiconductor device manufacturing processes. At least one external variable is identified. How the external variable impacts a semiconductor device manufacturing process is determined. A determination whether the impact of the external variable causes an appreciable impact on the semiconductor device manufacturing process is made. At least one control parameter of the semiconductor device manufacturing process is adjusted in response to the determination that the impact of the external variable causes an appreciable impact on the semiconductor device manufacturing process.
In another aspect of the present invention, an apparatus is provided for correction of machine disturbances for run-to-run control of semiconductor device manufacturing processes. The apparatus of the present invention comprises means for identifying at least one external variable, means for determining how said external variable impacts a semiconductor device manufacturing process, means for determining whether the impact of the external variable causes an appreciable impact on the semiconductor device manufacturing process, and means for adjusting at least one control parameter of the semiconductor device manufacturing process in response to the determination that the impact of the external variable causes an appreciable impact on the semiconductor device manufacturing process.